doc.: IEEE 802.11-15/0027r0
Submission
January 2015
Simulation-based evaluation of DSC in residential scenario
Date: 2015-JanAuthors:
M. Shahwaiz Afaqui (UPC)Slide 1
Name Affiliations Address Phone email
M. Shahwaiz Afaqui Technical University of Catalonia (UPC)
Edifici C4 Despatx 323 C/ Esteve Terrades, 7 08860 Castelldefels, Barcelona, Spain.
+34 93 41 37218
Eduard Garcia-Villegas
Technical University of Catalonia (UPC)
Edifici C4 Despatx 322 C/ Esteve Terrades, 7 08860 Castelldefels, Barcelona, Spain.
+34 93 41 37120
Elena Lopez-Aguilera
Technical University of Catalonia (UPC)
Edifici C4 Despatx 303 C/ Esteve Terrades, 7 08860 Castelldefels, Barcelona, Spain.
+34 93 41 37064
Graham Smith SR Technologies [email protected]
Daniel Camps i2CAT Foundation
+34 93 55 32633
doc.: IEEE 802.11-15/0027r0
Submission
Outline
1. Context
2. Simulation Environment: NS-3
3. DSC algorithm
4. Simulation scenarios and assumptions
5. Metrics used for evaluation
6. Selection of suitable parameters for DSC
7. Combining DSC with channel selection and rate control
8. Hybrid case A: Impact of DSC cells over legacy cells
9. Hybrid case B: Impact of DSC nodes over legacy nodes within cells
10. Worst case scenario (MCS0 & packet size of 1500 bytes)
11. Conclusions/next steps
12. References
13. Appendix
January 2015
M. Shahwaiz Afaqui (UPC)Slide 2
doc.: IEEE 802.11-15/0027r0
Submission
1. Context• One of the main objectives of IEEE 802.11ax standards is to improve efficiency in
scenarios with high density of AP and non-AP stations by,– increasing spectral frequency reuse.– managing interference in OBSS.
• It has been shown in previous presentations[1-11] that the use of DSC can increase the per-user throughput in dense scenarios.
• In this submission we, – investigate the performance of DSC,
• NS-3 simulator is used to measure the performance of DSC in dense WLAN network that contains multiple OBSS.
– recommend parameters to be employed for DSC algorithm.– study the impact of DSC cells over legacy cells.
January 2015
M. Shahwaiz Afaqui (UPC)Slide 3
doc.: IEEE 802.11-15/0027r0
Submission
2. Simulation Environment: NS-3• NS-3 is a simulator for Internet systems,
– It allows the study of protocols and network performance of large-scale systems in a controlled and scalable environment.
• Main characteristics,– Discrete event simulator– Packet level simulator (layer 2 and above)– Layered architecture– Free and open source– Frequent updates ( latest version ns 3.21- release date 17-09-2014)
• Large number of protocol implementations and models available,– TCP, UDP– IPV4, IPV6, static routing– IEEE 802.11 and variants, WiMAX, LTE– IEEE 802 physical layer– Mobility models and routing protocols– Ability to design indoor, outdoor or hybrid networks– etc.
January 2015
M. Shahwaiz Afaqui (UPC)Slide 4
doc.: IEEE 802.11-15/0027r0
Submission
2. Simulation Environment: NS-3• Challenges
– dense WLAN scenario with multiple OBSS generated in NS-3 where the simulation package is modified to,• allow STAs to measure the energy level of received beacon frames.• improve hybrid building pathloss model to accommodate floor
penetration losses.– modifications /new additions made to accommodate real time operation of
DSC algorithm.
• Limitations– MPDU aggregation is not yet implemented and thus not used within these
simulations.– IEEE 802.11ac model has not yet been developed and current results
focus on IEEE 802.11g/n.
January 2015
M. Shahwaiz Afaqui (UPC)Slide 5
doc.: IEEE 802.11-15/0027r0
Submission
3. DSC algorithm
• DSC varies CST levels at each station in a distributed manner,– stations near their respective AP can
have higher CST because interference from concurrent transmissions would have limited implications.
– stations further away can have lower CST because the probability of correct transmissions can be increased by reducing the presence of hidden nodes.
• Flow chart highlights the basic operation of DSC algorithm over non-AP stations in an infrastructure-based WLAN.
January 2015
M. Shahwaiz Afaqui (UPC)Slide 6
doc.: IEEE 802.11-15/0027r0
Submission
4. Simulation scenarios and assumptions• Topology
– multi-floor residential building,• 5 stories• 2×10 apartments per story.• Apartment size: 10m×10m×3m.
– 1 AP placed randomly in each apartment at 1.5m height.
– channel selected randomly for each cell.• Three channel scheme (1, 6, 11) 1/3 of
the cells share the same channel
– 5 STAs placed randomly around their respective AP.
January 2015
M. Shahwaiz Afaqui (UPC)Slide 7
doc.: IEEE 802.11-15/0027r0
Submission
• Frequency band: focused on 2.4GHz ,• Intended to investigate the impact of DSC in a band that is more restricted in dense
environments.
• Traffic: UDP CBR uplink transmission in saturation conditions is considered,• Worst case in terms of contention.
• Pathloss model: Hybrid Building Propagation loss model [12],• obtained through a combination of several well known pathloss including indoor (through
walls, floors) and outdoor (urban, suburban, open).
• We simulated specific scenarios (with same STA and AP positions) with and without utilizing the DSC.
• Additional simulation details are provided in the appendix.
4. Simulation scenarios and assumptions
January 2015
M. Shahwaiz Afaqui (UPC)Slide 8
doc.: IEEE 802.11-15/0027r0
Submission
5. Metrics used for evaluation
• Aggregate throughput and STA’s individual throughput
• Frame Error Rate (FER)– ratio of data frames received with errors to total data frames received.
• Fairness – calculated according to Jain’s fairness index [13].
• Number of hidden nodes– Hidden node: detected when a node that is located outside the sensing range of the
transmitter is able to interfere in the ongoing transmission from the transmitter to the receiver.
– a pair of hidden nodes is considered a single entry.
• Number of exposed nodes– Exposed node: detected when a node is needlessly silenced to concurrently transmit, even
though the node is not able to generate ample interference that could cause collisions at the receiver.
– a pair of exposed nodes is considered a single entry.
January 2015
M. Shahwaiz Afaqui (UPC)Slide 9
doc.: IEEE 802.11-15/0027r0
Submission
6. Selection of suitable parameters for DSC
• Observations:– throughput results indicate around 10 % improvement for all the cases over the
conventional IEEE 802.11 protocol.– maximum fairness benefits were achieved when lower values of Margin are used.
• Conclusions:– the proposed algorithm increases the aggregate throughput along with fairness.
5 10 15 20 250
2
4
6
8
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12
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16 RSSIDEC=4RSSIDEC=5RSSIDEC=6
Margin
% I
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t
5 10 15 20 250
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4
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18 RSSIDEC=4RSSIDEC=5RSSIDEC=6
Margin
% I
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in f
airn
ess
January 2015
M. Shahwaiz Afaqui (UPC)Slide 10
doc.: IEEE 802.11-15/0027r0
Submission
• Observations:– higher values of Margin and RSSIDec result in smaller FER degradation.– at higher Margin values, the increase in hidden nodes is smaller. – the presence of exposed nodes is driven to 0 by the DSC algorithm.
• Conclusions:– a consequence of the increased number of hidden nodes, the overall FER in network is
increased larger access delay.
5 10 15 20 250
5
10
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30 RSSIDEC=4RSSIDEC=5RSSIDEC=6
Margin
% I
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in F
ER
5 10 15 20 250
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500RSSIDEC=4RSSIDEC=5RSSIDEC=6
Margin
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6. Selection of suitable parameters for DSC
January 2015
M. Shahwaiz Afaqui (UPC)Slide 11
doc.: IEEE 802.11-15/0027r0
Submission
7. Combining DSC with channel selection and rate control (1/2)
• Observations:– scenarios where DSC is combined with optimal channel selection provide maximum
throughput gains of more than 20%.– DSC has more room for improvement when MCS is set randomly.– Fairness and throughput increased in all the scenarios when DSC is used.
• Conclusions:– Optimal channel selection has slightly larger impact on performance than DSC– DSC increases the aggregate throughput by fairly increasing throughput over all the
nodes.
RCHS+FMCS OPCHS+FMCS RCHS+RMCS OPCHS+RMCS0.5
0.6
0.7
0.8
0.9
1
Without DSCWith DSC
Fai
rnes
s
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35 RCHS+FMCSOPCHS+FMCSRCHS+RMCSOPCHS+RMCS
% I
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January 2015
M. Shahwaiz Afaqui (UPC)Slide 12
doc.: IEEE 802.11-15/0027r0
Submission
• Observations:– FER is slightly improved when optimal channel selection is used along with DSC.– % increase in hidden nodes is smaller while utilizing optimal channel selection.– with random channel selection, the increase in hidden nodes is around 150%. – 100% decrease in the number of exposed nodes is witnessed for all the cases.
• Conclusions:– the effect of increase in FER and the number of hidden nodes due to the DSC algorithm
can be reduced while utilizing optimal channel selection along with DSC.
RCHS+FMCS OPCHS+FMCS RCHS+RMCS OPCHS+RMCS0
0.1
0.2
0.3
0.4
0.5Without DSCWith DSC
FE
R
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180 RCHS+FMCSOPCHS+FMCSRCHS+RMCSOPCHS+RMCS
% I
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idde
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7. Combining DSC with channel selection and rate control (2/2)
January 2015
M. Shahwaiz Afaqui (UPC)Slide 13
doc.: IEEE 802.11-15/0027r0
Submission
8. Hybrid case A: Impact of DSC cells over legacy cells (1/3)
• Observations:– average throughput of DSC cells increases over the cost of decrease in average throughput of
non-DSC cells.– throughput gains for DSC cells are more evident in hybrid scenarios (i.e. DSC + non-DSC cells) .– average fairness in the network increases with the inclusion of DSC enabled cells.
• Conclusions:– overall average throughput and fairness are increased within the hybrid network due to DSC,
• Legacy cells/devices become less competitive.
0 20 40 60 80 1000
0.5
1
1.5
2
2.5
3
3.5
4
4.5All cells
DSC cells
non-DSC cells
% of DSC cells
Av
era
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hp
ut
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e
0 20 40 60 80 1000.64
0.65
0.66
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0.7
0.71
0.72
0.73
% of DSC cells
Ave
rage
fai
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January 2015
M. Shahwaiz Afaqui (UPC)Slide 14
doc.: IEEE 802.11-15/0027r0
Submission
0 20 40 60 80 1000
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45 All cellsDSC cellsnon-DSC cells
% of DSC cells
Ave
rage
FE
R
• Observation:– average FER of DSC cells increases whereas the FER of non-DSC cells remains
approximately consistent.
• Conclusion:– overall FER in the network increases with the increase in DSC cells.
8. Hybrid case A: Impact of DSC cells over legacy cells (2/3)
January 2015
M. Shahwaiz Afaqui (UPC)Slide 15
doc.: IEEE 802.11-15/0027r0
Submission
• Observations:– % increase in hidden nodes is greater for more number of DSC cells.– maximum % decrease in exposed nodes is witnessed when all cells are DSC enabled.
• Conclusions:– the FER in the network is increased due to increased number of hidden nodes.– DSC increases fairness in the network by reducing the number of exposed nodes.
20 40 60 80 1000
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160
180
% of DSC cells
% i
ncr
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20 40 60 80 1000
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% of DSC cells
% d
ecre
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8. Hybrid case A: Impact of DSC cells over legacy cells (3/3)
January 2015
M. Shahwaiz Afaqui (UPC)Slide 16
doc.: IEEE 802.11-15/0027r0
Submission
9. Hybrid case B: Impact of DSC nodes over legacy nodes within cells (1/3)
0 20 40 60 80 1000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
% of nodes using DSC per cell
Ave
rage
fai
rnes
s
0 20 40 60 80 1000
1
2
3
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5
6
All nodes
DSC nodes
Non-DSC nodes
% of nodes using DSC per cell
Ave
rage
thr
ough
put p
er n
ode
• Observations:– average throughput of DSC nodes increases over the cost of decrease in throughput of non-DSC
nodes.– throughput gains for DSC nodes are more evident than performance losses for non-DSC nodes.– average fairness in the network was reduced for some hybrid scenarios (20% to 60% DSC nodes).
• Conclusions:– overall average throughput of the network is increased due to DSC, at the cost of noticeable
performance degradation for legacy devices.
January 2015
M. Shahwaiz Afaqui (UPC)Slide 17
doc.: IEEE 802.11-15/0027r0
Submission
0 20 40 60 80 1000
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
All nodesDSC nodesnon-DSC nodes
% of nodes using DSC per cell
Ave
rage
FE
R
9. Hybrid case B: Impact of DSC nodes over legacy nodes within cells (2/3)
• Observation:– average FER of DSC and non-DSC nodes increase with an increase in % nodes using
DSC in a cell.
• Conclusion:– overall FER in the network (for all nodes) increases with the increase in DSC enabled
nodes.
January 2015
M. Shahwaiz Afaqui (UPC)Slide 18
doc.: IEEE 802.11-15/0027r0
Submission
20 40 60 80 1000
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% of nodes using DSC per cell
% in
crea
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% of nodes using DSC per cell
% d
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9. Hybrid case B: Impact of DSC nodes over legacy nodes within cells (3/3)
• Observations:– % increase in hidden nodes is greater for more number of DSC nodes.– for the hybrid scenario, the % increase in hidden nodes is less than the case where all
nodes are DSC enabled within a cell.– maximum % decrease in exposed nodes is witnessed when all cells utilize DSC.
• Conclusions:– due to increased number of hidden nodes, the FER in the network is increased.– DSC increases fairness in the network by reducing the number of exposed nodes.
January 2015
M. Shahwaiz Afaqui (UPC)Slide 19
doc.: IEEE 802.11-15/0027r0
Submission
10. Worst case scenario (MCS0 & packet size of 1500 bytes) (1/2)
• Observations:– scenario where DSC is combined with optimal channel selection provides maximum
throughput gains of around 35%.– fairness is increased in all the scenarios when DSC is used.
• Conclusions:– DSC increases the aggregate throughput by fairly increasing throughput over all the
nodes.– % increase in throughput for DSC plus optimal channel selection cells is considerable
even under difficult network conditions.
0
5
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15
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30
35
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45 MCS0+ps1500+RCHS
MCS0+ps1500+OPCHS
% in
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MCS0+ps1500+RCHS MCS0+ps1500+OPCHS0.5
0.6
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1 Without DSCWith DSC
Fai
rnes
s
January 2015
M. Shahwaiz Afaqui (UPC)Slide 20
doc.: IEEE 802.11-15/0027r0
Submission
• Observations:– difference of average FER per node between DSC enabled and legacy nodes is notable
when optimal channel selection is utilized.– % increase in hidden nodes is less while utilizing optimal channel selection.– almost 100% decrease in the number of exposed nodes is witnessed for all the cases.
• Conclusions:– relatively small difference in FER is observed between the network consisting of optimal
channel selection and random channel selection.– optimal channel selection helps to reduce the number of hidden nodes.
10. Worst case scenario (MCS0 & packet size of 1500 bytes) (2/2)
MCS0+ps1500+RCHS MCS0+ps1500+OPCHS0
0.1
0.2
0.3
0.4
0.5Without DSCWith DSC
FE
R
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MCS0+ps1500+OPCHS
% in
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s
January 2015
M. Shahwaiz Afaqui (UPC)Slide 21
doc.: IEEE 802.11-15/0027r0
Submission
11. Conclusions/next steps• DSC scheme provides improvements in throughput and fairness in all cases
• Based on the reduction of exposed nodes
• DSC also increases number of hidden nodes and FER.
• DSC makes more sense (i.e. provides larger improvements) in worse conditions
• Higher contention• Slower STAs
• Margin of 20 and RSSIDec of 6 are observed to create a balance between the negative and positive aspects of DSC.
• Channel selection and rate control can improve the positive effects of DSC scheme.
• For Hybrid case A (DSC cells vs non-DSC cells): notable throughput gains for DSC cells at the cost of slight degradation for non-DSC cells.
• For Hybrid case B (DSC STAs vs. non-DSC STAs in the same cell): fairness results indicate the coexistence problem between DSC and legacy IEEE 802.11 nodes within the cells.
• Next steps,
• Repeat study in different scenarios.• Analyze the impact of DSC in uplink plus downlink traffic.• Study the effects of DSC algorithm over a network operating in 5GHz.
January 2015
M. Shahwaiz Afaqui (UPC)Slide 22
doc.: IEEE 802.11-15/0027r0
Submission
12. References
1) Graham Smith, DSP Group, 11-13-1290-01 Dynamic Sensitivity Control for HEW
2) Graham Smith, DSP Group, 11-13-1487-02 Dense Apartment Complex Capacity Improvements with Channel selection and Dynamic Sensitivity Control
3) Graham Smith, DSP Group, 11-13-1489-05 Airport Capacity Analysis
4) Graham Smith, DSP Group, 11-14-0045-02 E-Education Analysis
5) Graham Smith, DSP Group, 11-14-0058-01 Pico Cell Use Case Analysis
6) Graham Smith, DSP Group, 11-14-0294-02 Dynamic Sensitivity Control Channel Selection and Legacy Sharing
7) Graham Smith, DSP Group, 11-14-0365-01 Dynamic Sensitivity Control Implementation
8) Graham Smith, DSP Group, 11-14-0328-02 Dense Apartment Complex Throughput Calculations
9) Graham Smith, DSP Group, 11-14-0779-00 Dynamic Sensitivity Control Practical Usage
10) Imad Jamil, Orange, 11-14-0523-00 Mac Simulation Results for DSC and TPC
11) William Carney, Sony, 11-14-0854-00 DSC and Legacy Coexistence
12) Hybrid buildings propagation loss model: ns3-design document. [Online]. Available: http://www.nsnam.org/docs/models/html/buildingsdesign.html
13) J. R., “Fairness: How to measure quantitatively?” ATM Forum/94-0881, Sept. 1994.
January 2015
M. Shahwaiz Afaqui (UPC)Slide 23
doc.: IEEE 802.11-15/0027r0
Submission
13. Appendix
January 2015
M. Shahwaiz Afaqui (UPC)Slide 24
doc.: IEEE 802.11-15/0027r0
Submission
Simulation assumptions• PHY parameters
Parameters4 Values Parameters Values
Wireless Standard IEEE 802.11g and IEEE 802.11n
Packet size 1000bytes
Frequency band 2.4 GHz STA TX power 16dBm
Physical transmission rate for IEEE 802.11g
24Mbps Transmission gain 1dB
Physical transmission rate for IEEE 802.11n
i. 7.2Mbpsii. 28.9Mbpsiii. 72.2Mbps
Reception gain 1dB
Channel width 20MHz Noise figure 7dB
Propagation delay model
Constant speed propagation delay
Energy detection threshold -78dBm
Propagation loss model Hybrid buildings propagation loss
Initial CCA threshold -80dBm
Wall penetration loss 12dB Guard interval Short
Floor penetration loss 17dB Data preamble Short
January 2015
M. Shahwaiz Afaqui (UPC)Slide 25
doc.: IEEE 802.11-15/0027r0
Submission
• MAC parameters
Parameters Values Parameters Values
Access protocol EDCA Retransmission attempts 16
RTS/CTS Disabled Maximum missed beacons for re-association
10000
Association 100% STAs associated to AP in an Apartment
Active probing Disabled
QOS Enabled Traffic model Best effort
Aggregation Disabled
• Simulation parameters
Parameters Values Parameters Values
Simulation time 25 seconds Simulations for each hybrid case
24
Confidence interval 95% Simulations for non-DSC network
24
January 2015
M. Shahwaiz Afaqui (UPC)Slide 26